No problem....top tier used to be rare around Detroit (only Shell) when the designation was new, but is really pretty common. And yeah, a run down place might have some rusty tanks.

I prefer newer stations that move a lot of gasoline thru their tanks. (Costco is constantly pumping gas out of every pump, has top tier, and is cheaper than most everyone else....so I usually buy my gas there.) But there are a LOT of Shell, Mobil, Marathon, Sunoco, Valero, and BP stations around and I'm quite sure to find these when traveling. Getting a good slug of detergent in your normal gas beats having to pay for additives...

 

I may try some, but like you, I prefer new station for the same reason...old tanks, dispite filters, I prefer newer stations.